1. Field of the Invention
The present invention relates to a developer container containing a developer and, more particularly, to a developer container having a sealing member for preventing a leak of a developer. This developer container is preferably used in an image forming apparatus such as an electrophotographic copying machine or a laser beam printer.
2. Related Background Art
A detachable toner cartridge of an image forming apparatus has a structure in which, in order to prevent a leak of toner as a developer when the toner cartridge is installed or removed or while it is used, a gap between a container containing the developer and an assembling member assembled to this container is sealed by adhering a urethane sponge or applying a liquid elastomer to the gap (Japanese Patent Application Laid-Open Nos. 4-289869 and 4-9869).
To seal the gap by adhering the urethane sponge, the sponge is manually adhered to the container or the like by using, e.g., a double-coated tape adhered to the sponge beforehand. This work is labor intensive, and the adhesion is difficult and time-consuming.
If the purpose is sealing with no sliding of the parts, the use of sealing by application of a liquid elastomer is known. This application of a liquid elastomer uses automatic application using a dispenser. This automatic application has a working efficiency higher than that of manual work. In a method in which a liquid elastomer is linearly applied to a container as a junction surface with respect to an assembling member, a dispenser is mounted on an NC robot, and the liquid elastomer is discharged in constant amount while the position of the dispenser is controlled along the shape of the container. In this method, the application area has a closed loop locus having the start and end points at the same position. In this application area having a closed loop locus, application is performed such that the start and end points are the same or overlap each other. Even if the application amounts at the start and end points are different, it is possible to ensure a sufficient application amount and high sealing properties.
Possible causes of variations in the application amount are as follows:
Unfortunately, when a liquid elastomer is applied to a gap between a container containing a developer and an assembling member, the application locus cannot be a closed loop depending on the shape of this assembling member. If application is performed by a linear locus, a large difference is produced between the application amounts within the range of the start and end points in the application area, for the reasons explained below.
That is, liquid elastomers are classified into one-component thermoplastic type, two-component type which solidifies by mixing, and the like. Any of these types is a medium- to high-viscosity liquid. When application is performed using a dispenser, the actual application amount largely varies with respect to the opening/closing of a nozzle, because the application amounts at the start and end points in the application area are unstable owing to low discharge response caused by viscosity, the presence/absence of solid matter (the residue of previous application) at the tip of the nozzle, and the like. If the application amount is small, no sufficient sealing properties can be ensured, resulting in a defective product with a toner leak.
To stabilize the initial application amount, it is also possible to combine a method which performs preliminary discharge in a location other than the application area immediately before application. However, this increases the number of operation steps before application, and lowers the productivity by prolonging the tact time.
Alternatively, a liquid elastomer (two-component reaction type) disclosed in Japanese Patent Application Laid-Open No. 4-289869 is applied or injected as a sealing agent and aged for foaming, and parts are assembled after that.
As a liquid elastomer requiring no aging for foaming and capable of being injected into a gap after parts assembly, a one-component elastomer (trade name: xe2x80x9cFOAM MELTxe2x80x9d) obtained by liquefying thermoplastic synthetic rubber with heat and mixing an inert gas is known. This one-component elastomer is a medium- to high-viscosity liquid and must be maintained in a high-temperature liquid state immediately before injection. A dispenser used in the injection is a valve unit with a circulating hose having a built-in heater. The elastomer is discharged by opening/closing the on-off valve in the end portion of the dispenser.
In the above prior art, however, the valve unit structure with a circulating hose having a built-in heater is used to inject the liquid elastomer to the gap between the container containing a developer and an assembling member. Since the size of this dispenser is large, the space is limited with respect to the injection position of the container. Also, the impingement position of the liquid elastomer discharged from the nozzle varies owing to the dispenser internal pressure, the presence/absence of solid matter (the residue of previous application) at the nozzle tip, and the state of the nozzle opening surface.
If the impingement position of the liquid elastomer deviates to make it impossible to fill an injection groove with the liquid elastomer, no sufficient sealing properties can be assured, resulting in a defective product with a toner leak.
FIG. 12 shows the elastomer application state in this case. The injection position of a dispenser 11 with respect to a container 1 is set above an elastomer injection area a shown in FIG. 12 (this injection area a is a gap between a blade 2 and the container 1). That portion extending from a nozzle 17, which is indicated by the dotted lines is an elastomer impingement area a. This elastomer impingement area a has the same width as the elastomer injection area a. However, if impingement area greater than injection area, the elastomer cannot be injected into a predetermined area in some instances, as indicated by an elastomer 19.
In addition, with the recent increase in required image quality, the toner particle size is being more and more decreased. This makes it difficult to well prevent a toner leak only by simply injecting a liquid elastomer into a gap between toner cartridge parts assembled beforehand.
It is an object of the present invention to provide a developer container which reliably prevents a leak of a developer.
It is another object of the present invention to provide a developer container capable of improving the productivity for the formation of a sealing member.
It is still another object of the present invention to provide a developer container capable of reliably preventing a leak of toner having a small particle size, regardless of the dimensional tolerance or assembly tolerance of parts.
Other objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.